Options for thermally insulating window coverings?
We have a 1974 4-bedroom Colonial in New Hampshire (climate Zone 5) with some old plastic blinds that need to be replaced/upgraded. My wife offered to sew up some fabric curtains to replace them, but I wanted to ask here first and see what options are on the market for reducing heat losses while improving aesthetics with better blinds.
I know there are some windows treatments with edge-sealing details to break the convective cooling loop between the cold window and the warm room. We had some cellular blinds at a prior house that we liked but it was in a hot climate so shade was more important than thermally insulating.
Windows are Anderson double-hung vinyl frames, ~15 years old. I have noticed some condensation between panes and at the corners where cold air is leaking path the fin sweeps.
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I made an insulated rollup shade for a picture window. It worked reasonably well but it is very hard to keep humid air out of the space between the shade and the window. I put up with buildup of ice on the window (zone 5) if I left it down for long. Cozycurtains.com sells premade shades with the built-in magnets. They have a mylar=like vapor barrie I believe.
They work great but understand you are playing with a double edged sword.
Yes you will cut the heat loss thru the window. The more heat you keep away from the glass the colder it will get when it falls below the dew point of the air in your house things will get wet. Most vinyl window have drywall returns that but up against the window and is soaking up the water. Even when looks OK on the surface the back side can be growing mold. If your shade works well enough and it gets cold enough ice will build up on your windows it will melt sooner or later can your window sills that that much water?
Are you willing to dry out your hose to 30% and lower the dew point? Will you get rid of your house plants? Take fewer showers? Install and run ERV?
Walt
Many years ago I installed double pleated shades with side tracks to keep air from circulating behind the shades. They have been wonderful. On a cold winter night in Vermont, if I sat in front of the windows with the shades up I could feel the cold radiating through the window, while with the shades down it is much more comfortable.
I have not had a problem with condensation on the windows -- I think that because the air does not circulate there is not much water in the small amount of air between the window and the shade at the time the shade is lowered.
On my first batch of shades I made the mistake of saving a little money and getting the old fashioned strings that rely on friction and momentum to lower the shades. Although they can be made to work they are often a pain. For the second batch I got looped strings so that you pull the shades up and down and they work much better for a small additional charge.
Also be sure to measure the width of the windows very carefully. If the window frame is out of square by more than a small fraction of an inch and the shades are too wide at the top or bottom you may not be able to use the side tracks.
My side tracks were called comfort tracks but they may now be called slumber shades. I got mine online from Blinds Chalet.